use strict;
use warnings;
use feature 'say';

my @array1 = ("A2","A5","C1","G0","T3","T4");
my @array2 = ("A2","A3","A5","G1","G0","G4");

my %lookup = map { $_ => 1 } @array1;

for my $thing ( @array2 ) {
    say "I found $thing" if $lookup{ $thing };
}

__END__